Dishing prevention dummy structures for semiconductor devices

ABSTRACT

In some embodiments, an integrated circuit is provided. The integrated circuit may include an inner ring-shaped isolation structure that is disposed in a semiconductor substrate. Further, the inner-ring shaped isolation structure may demarcate a device region. An inner ring-shaped well is disposed in the semiconductor substrate and surrounds the inner ring-shaped isolation structure. A plurality of dummy gates are arranged over the inner ring-shaped well. Moreover, the plurality of dummy gates are arranged within an interlayer dielectric layer.

REFERENCE TO RELATED APPLICATIONS

This Application is a Continuation of U.S. application Ser. No. 16/683,530, filed on Nov. 14, 2019, which is a Continuation of U.S. application Ser. No. 16/437,137, filed on Jun. 11, 2019 (now U.S. Pat. No. 10,516,029, issued on Dec. 24, 2019), which is a Continuation of U.S. application Ser. No. 15/964,572, filed on Apr. 27, 2018 (now U.S. Pat. No. 10,340,357, issued on Jul. 2, 2019), which claims the benefit of U.S. Provisional Application number 62/562,564, filed on Sep. 25, 2017. The contents of the above-referenced Patent Applications are hereby incorporated by reference in their entirety.

BACKGROUND

Integrated chips comprise millions or billions of transistor devices. Modern day integrated chips generally comprise a variety of transistors that are capable of operating a different voltages. High voltage devices are widely used in power management, regulators, battery protectors, DC motors, automotive circuits, panel display drivers, etc. On the other hand, low voltage devices are typically used for logic cores, microprocessors, and microcontrollers. Some modern integrated circuit (IC) designs integrate both high voltage and low voltage devices on a single chip. In both high voltage and low voltage technologies, functional density (e.g., the number of devices per chip area) has generally increased while feature size (e.g., the smallest component (or line) that can be created using a fabrication process) has decreased. However, the increase in functional density and decrease in feature size has caused both low voltage and high voltage devices to suffer leakage and other undesirable dimensional based effects.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 illustrates a top view of some embodiments of an integrated circuit comprising first and second IC regions having dishing prevention dummy gates.

FIG. 2 illustrates a cross-sectional view of some embodiments of an integrated circuit comprising first and second IC regions having dishing prevention dummy gates.

FIG. 3A illustrates a cross-sectional view of some more detailed embodiments of an integrated circuit comprising first and second IC regions having dishing prevention dummy gates.

FIG. 3B illustrates a cross-sectional view of some embodiments of an integrated circuit comprising a first IC region having dishing prevention dummy gates and a second IC region having dishing prevention dummy gates disposed proximate a third device region.

FIGS. 4-19 illustrate a series of cross-sectional views of some embodiments of a method for forming an integrated circuit comprising first and second IC regions having dishing prevention dummy gates.

FIG. 20 illustrates a flowchart of some embodiments of the method for forming an integrated circuit comprising first and second IC regions having dishing prevention dummy gates.

DETAILED DESCRIPTION

The present disclosure provides many different embodiments, or examples, for implementing different features of this disclosure. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper”, and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device or apparatus in use or operation in addition to the orientation depicted in the figures. The device or apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly. Even more, the terms “first”, “second”, “third”, “fourth”, and the like are merely generic identifiers and, as such, may be interchanged in various embodiments. For example, while an element (e.g., an etch, a dielectric layer, or a substrate) may be referred to as a “first” element in some embodiments, the element may be referred to as a “second” element in other embodiments.

As the feature size of integrated chip devices has decreased, electrical isolation between adjacent devices has become more difficult. Generally, electrical isolation is achieved by way of isolation structures disposed within a substrate. For example, isolation between adjacent devices can be achieved by way of shallow trench isolation (STI) structures and/or by guard rings. While, such structures generally provide for good electrical isolation between adjacent devices, other leakage paths also exist.

For example, during the fabrication of semiconductor devices, chemical-mechanical planarization (CMP) processes are widely used to form planar surfaces. When CMP processes are performed on interfaces having different materials, the different materials may be removed at different rates. The removal of different materials at different rates will result in some areas of the interface being recessed relative to other areas, an effect commonly known as “dishing.” When a CMP process is performed on a dielectric layer that is disposed over a first and second plurality of devices, the CMP process will remove portions of the dielectric layer, for example, to expose underlying features of the devices (e.g., a sacrificial gate) for subsequent processing (e.g., etching for a replacement poly-gate (RPG) process) and/or provide a uniform height for the underlying features (e.g., to form a uniform metal gate height) of the devices and the dielectric layer.

However, due to the process parameters of the CMP process(es) (e.g., chemical slurry composition, pressure, velocity, time, etc.) and the various types of materials disposed within the dielectric layer (e.g., dielectric, metal, polysilicon, etc.), the CMP process(es) may cause dishing in the dielectric layer (as the various materials are removed at different rates during the CMP process) between adjacent devices. During a subsequent metallization process (e.g., replacing polysilicon gates with a conductive material), the lower regions of the dielectric layer may be filled with a conductive metal, resulting in leakage paths between the adjacent devices. In the case of high voltage devices, this problem can be aggravated due to dielectric breakdown caused by the high voltages of the devices. In some severe instances, the dishing may cause improperly functioning devices.

The present disclosure pertains to an integrated circuit having a first IC region and a second IC region. The first IC region comprises a first device region (e.g., a low voltage region) that has a plurality of first devices. The second IC region comprises a second device region (e.g., a mid voltage region) that has a plurality of second devices. The first IC region has a first inner ring-shaped well (i.e., a first guard ring) that surrounds the first device region and a first outer ring-shaped well that surrounds the first inner ring-shaped well. The second IC region has a second inner ring-shaped well (i.e., a second guard ring) that surround the second device region and a second outer ring-shaped well that surrounds the second inner ring-shaped well. A plurality of dishing prevention dummy gates are disposed within a dielectric layer over an upper surface of both the first IC region and the second IC region. The dishing prevention dummy gates provide structural support during fabrication of the IC to mitigate the amount of dishing of the dielectric layer. Accordingly, the performance of the underlying devices may be improved and the cost of manufacturing ICs may be reduced.

FIG. 1 illustrates a top view of some embodiments of an integrated circuit 100 comprising a first IC region having dishing prevention dummy gates and a second IC region having dishing prevention dummy gates.

The integrated circuit (IC) 100 has a first IC region 112 a having a first device region 102 a and a second IC region 112 b having a second device region 102 b. In some embodiments, the first device region 102 a comprises a plurality of first devices 104 a, and the second device region 102 b comprises a plurality of second devices 104 b. In some embodiments, the first devices 104 a and the second devices 104 b may be low voltage devices (e.g., operating voltage of approximately 1.2 eV), mid-voltage devices (e.g., operating voltage of approximately 6.0 eV), or high voltage devices (e.g., operating voltage of approximately 1,000 eV). In yet further embodiments, the first device region 102 a may comprise one type of devices (e.g., low voltage, mid-voltage, or high voltage) and the second device region 102 b may comprise one type of device. The low voltage, mid-voltage, or high voltage devices may be for example, metal-oxide-semiconductor field effect transistors (MOSFETs), complementary MOS (CMOS) transistors, laterally diffused MOS (LDMOS) transistors, high power MOS transistors, FinFET, and/or other types of devices.

The first device region 102 a is surrounded by a first inner ring-shaped well 106 a. The first inner ring-shaped well 106 a is disposed within an underlying semiconductor substrate and comprises a first doping type (e.g., n-type). The first inner ring-shaped well 106 a is separated from the first device region 102 a by a first inner isolation structure 107 a (e.g., a shallow trench isolation (STI)). The first inner ring-shaped well 106 a comprises a first inner highly doped region 111 a (e.g., n+) having the first doping type and is disposed between the first inner isolation structure 107 a and a first outer isolation structure 109 a. In some embodiments, a contact (not shown) is coupled to the first inner highly doped region 111 a of the first inner ring-shaped well 106 a and is configured to provide a first electric potential (e.g., a low relative voltage or a high relative voltage). Accordingly, the first inner ring-shaped well 106 a may act as a protection element (i.e., a first guard ring) for devices disposed on the IC 100 by collecting unwanted electrical signals that may propagate in/out of the first device region 102 a and disrupt (e.g., latch-up, unwanted activation, etc.) the function of the devices disposed on the IC.

In some embodiments, the first inner ring-shaped well 106 a has a first inner ring-shaped well thickness, t₁, which defines a width of the first inner ring-shaped well 106 a and may be substantially the same at various points around the first device region 102 a, measured from a perimeter of the first device region 102 a to a perimeter of the first inner ring-shaped well 106 a. The first inner ring-shaped well thickness, t₁, may be based, at least in part, on the type of devices (e.g., low voltage, mid-voltage, or high voltage) disposed within the first device region 102 a.

In some embodiments, the first inner ring-shaped well 106 a is surrounded by a first outer ring-shaped well 108 a. In yet further embodiments, the first inner ring shaped well 106 a and the first outer ring-shaped well 108 a are concentric about a first center point 110 a of the first device region 102 a. The first outer ring-shaped well 108 a is disposed within the underlying semiconductor substrate and comprises a second doping type (e.g., p-type) that is opposite the first doping type. The first outer ring-shaped well 108 a is separated from the first inner ring-shaped well 106 a by a first outer isolation structure 109 a (e.g., STI). The first outer ring-shaped well 108 a comprises a first outer highly doped region 113 a (e.g., p+) having the second doping type and is disposed between the first outer isolation structure 109 a and the perimeter of the first IC region 112 a. In some embodiments, a contact (not shown) is coupled to the first outer highly doped region 113 a of the first outer ring-shaped well 108 a and is configured to provide a second electric potential opposite the first electric potential (e.g., either a high relative voltage or a low relative voltage). Accordingly, the first inner ring-shaped well 106 a and the first outer ring-shaped well 108 a act as protection elements (i.e., guard rings) for devices disposed on the IC 100 by providing a p-n junction isolation that prevents unwanted current from flowing in/out the first device region 102 a and disrupting the function of devices disposed on the IC 100.

The first outer ring-shaped well 108 a has a first outer ring-shaped well thickness, t₂, which defines a width of the first outer ring-shaped well 108 a and may be substantially the same at various points around the first inner ring-shaped well 106 a, measured from a perimeter of the first inner ring-shaped well 106 a to a perimeter of the first outer ring-shaped well 106 b. The first outer ring-shaped well thickness, t₂, may be based, at least in part, on the type of devices (e.g., low voltage, mid-voltage, or high voltage) disposed within the first device region 102 a. In some embodiments, the first inner ring-shaped well thickness, t₁, is substantially similar to the first outer ring-shaped well thickness, t₂. In yet other embodiments, the first inner ring-shaped well thickness, t₁, may be greater than the first outer ring-shaped well thickness, t₂. For example, the first inner ring-shaped well thickness, t₁, may be twice the first outer ring-shaped well thickness, t₂.

In some embodiments, the second device region 102 b and the second devices 104 b are arranged in a similar manner as the first device region 102 a and the first devices 104 a. For example, the second device region 102 b is surrounded by a second inner ring-shaped well 106 b, and the second inner ring-shaped well 106 b is surrounded by a second outer ring-shaped well 108 b. In some embodiments, the perimeter of the second outer ring-shaped well 108 b defines the perimeter of the second IC region 112 b. The second inner ring-shaped well 106 b has a thickness, t₃, and the second outer ring-shaped well 108 b has a thickness, t₄.

A plurality of dishing prevention dummy gates 114 are disposed over an upper surface of the first inner ring-shaped well 106 a, the first outer ring-shaped well 108 a, first inner isolation structure 107 a, and the first outer isolation structure 109 a. In some embodiments, the plurality of dishing prevention dummy gates 114 are disposed partially over or completely over the upper surface of the first inner ring-shaped well 106 a, the first outer ring-shaped well 108 a, first inner isolation structure 107 a, and the first outer isolation structure 109 a in a vertical direction. In addition, a plurality of dishing prevention dummy gates 114 are disposed over an upper surface of the second inner ring-shaped well 106 b, the second outer ring-shaped well 108 b, a second inner isolation structure 107 b, and a second outer isolation structure 109 b. In some embodiments, the plurality of dishing prevention dummy gates 114 are disposed partially over or completely over the upper surface of the second inner ring-shaped well 106 b, the second outer ring-shaped well 108 b, a second inner isolation structure 107 b, and a second outer isolation structure 109 b in a vertical direction. In further embodiments, the dishing prevention dummy gates 114 comprise a conductive material (e.g., metal, polysilicon, silicide, etc.). In further embodiments, the dishing prevention dummy gates 114 are electrically floating (e.g., a voltage is not applied to the dummy gates 114 during operation of the integrated circuit 100).

Further, while the dishing prevention dummy gates 114 are shown as quadrilaterals, it will be appreciated that the dishing prevention dummy gates 114 may have varying shapes and sizes. In some embodiments, the varying shapes and sizes may be based, at least in part, on the type of devices (e.g., low voltage, mid-voltage, or high voltage) disposed within the first device region 102 a and/or the second device region 102 b, or on the composition of the material (e.g., polysilicon, aluminum, tantalum, copper, etc.) of dishing prevention dummy gates 114. By basing the varying shapes and sizes of the dishing prevention dummy gates 114 on the foregoing properties, the dishing prevention dummy gates 114 may prevent unwanted dishing from occurring over the first device region 102 a and/or the second device region 102 b during a subsequent CMP process by acting as support pillars for a surrounding material (e.g., a dielectric material disposed over the first devices 104 a disposed in the first device region 102 a). Accordingly, by reducing the amount of dishing, the performance of the first devices 104 a and the second devices 104 b may be improved and the cost of manufacturing the IC 100 may be reduced.

FIG. 2 illustrates a cross-sectional view of some embodiments of an integrated circuit 200 comprising first and second IC regions having dishing prevention dummy gates.

The integrated circuit 200 comprises a semiconductor substrate 202 including the first inner ring-shaped well 106 a, the first outer ring-shaped well 108 a, the second inner ring-shaped well 106 b, and the second outer ring-shaped well 108 b. The semiconductor substrate 202 may comprise any type of semiconductor body (e.g., monocrystalline silicon/CMOS bulk, silicon-germanium (SiGe), silicon on insulator (SOI), etc.) and may be doped with the second doping type (e.g., p-type). The first inner ring-shaped well 106a may be a continuous ring-shaped region of the semiconductor substrate 202 that surrounds the first device region 102 a and comprises the first doping type (e.g., n-type). The ring-shaped region of the first inner ring-shaped well 106 a may be, for example, a circle, semi-circle, ellipse, quadrilateral, etc. In some embodiments, the first inner ring-shaped well 106 a extends below a bottom surface of the first inner isolation structure 107 a. The first inner ring-shaped well 106 a further comprises a first inner highly doped region of the first inner highly doped region 111 a, to which a contact (not shown) may be coupled. The first inner ring-shaped well 106 a is separated from the first device region 102 a by the first inner isolation structure 107 a. The first inner isolation structure 107 a may be, for example, a circle, semi-circle, ellipse, quadrilateral, etc. In some embodiments, the first inner isolation structure 107 a may be concentric about the first device region 102 a.

The first device region 102 a includes a first device well 206 a. In some embodiments, the first device well 206 a may be disposed within a first deep well 212 a that underlies the first device well 206 a. The first device well 206 a comprises a doping type (e.g., n-type or p-type) that depends on the function of the first device 104 a. In some embodiments, the first device well 206 a is separated from the first inner ring-shaped well 106 a by the first inner isolation structure 107 a. On the other hand, the first deep well 212 a may extend below the first device region 102 a, the first inner ring-shaped well 106 a, and a portion of the first outer isolation structure 109 a to contact the first outer ring-shaped well 108 a below a bottom surface of the first outer isolation structure 109 a. The first deep well 212 a comprises the first doping type (e.g., n-type).

Further, a pair of source/drain regions 216 laterally spaced from one another are arranged in the first device well 206 a. Moreover, a pair of source/drain extensions 218 are laterally spaced and disposed between the pair of source/drain regions 216 in the first device well 206 a. For clarity in the figures, a single first device well region 206 a is depicted in the first device region 102 a, and one pair of the pair of source/drain extension 218 is labeled. However, because the first device region 102 a may comprise a plurality of first devices 104 a, the first device region 102 a may comprise a plurality of first device well regions 206 a disposed throughout the first device region 102 a each having a pair of source/drain regions 216 and a pair of source/drain extensions 218, in which the doping may vary depending on the doping type of the first device well 206 a.

In some embodiments, the first outer ring-shaped well 108 a is a continuous ring-shaped region of the semiconductor substrate 202 that surrounds the first inner ring-shaped well 106 a and comprises the second doping type (e.g., p-type), which is different than the first doping type. The ring-shaped region of the first outer ring-shaped well 108 a may be, for example, a circle, semi-circle, ellipse, quadrilateral, etc. In some embodiments, the first outer ring-shaped well 108 a extends below a bottom surface of the first outer isolation structure 109 a and contacts a portion of the first inner ring-shaped well 106 a. The first outer ring-shaped well 108 a further comprises a first outer highly doped region 113 a of the first outer ring-shaped well 108 a, in which a contact (not shown) may be coupled. The first outer ring-shaped well 108 a is separated from the first inner ring-shaped well 106 a by the first outer isolation structure 109 a. The first outer isolation structure 109 a may be, for example, a circle, semi-circle, ellipse, quadrilateral, etc. In some embodiments, the first outer isolation structure 109 a may be concentric about the first outer ring-shaped well 108 a. In some embodiments, a first IC region isolation structure 236 a (e.g., STI) is disposed on a first side of the first outer ring-shaped well 108 a. In some embodiments, the first outer ring-shaped well 108 a and the second outer ring-shaped well 108 bshare a common doping region disposed between the first IC region 112 a and the second IC region 112 b. In such an embodiment, a mid-point of the common doping region may define a side of the first IC region 112 a and a side of the second IC region 112 b.

A device gate electrode 222 is disposed over the first device well 206 a and is separated from the semiconductor substrate 202 by a device gate dielectric 220. Sidewall spacers 224 are disposed along sidewalls of the device gate electrode 222 and the device gate dielectric 220. The device gate electrode 222, the device gate dielectric 220, and the sidewall spacers 224 are disposed within an interlayer dielectric (ILD) layer 204. The ILD layer 204 may comprise, for example, phosphosilicate glass (PSG), borophosphosilicate glass (BPSG), silicon dioxide (SiO₂), or some other suitable dielectric.

In some embodiments, the first devices 104 a may be low voltage devices and have a low voltage gate dielectric 220, a low voltage gate electrode 222, and sidewall spacers 224. On the other hand, in further embodiments, the second device 104 b may be a mid-voltage device having a mid-voltage gate dielectric 226, a mid-voltage gate electrode 228, and sidewall spacers 224, a pair of source/drain regions 216 disposed in the second device well 206 b, a pair of source/drain extensions 218 disposed in the second device well 206 b, and the second device well 206 b. In some embodiments, the low voltage gate electrode 222 and the mid-voltage gate electrode 228 comprise a conductive material (e.g., aluminum, copper, tantalum, or some other suitable material).

A plurality of dishing prevention dummy gates 114 are disposed within the ILD layer 204. The dishing prevention dummy gates 114 are arranged over the semiconductor substrate 202 and are positioned over various regions of the first IC region 112 a and the second IC region 112 b. In some embodiments, dishing prevention dummy gates 114 are arranged over the first/second inner isolation structures 107 a/107 b, the first/second outer isolation structures 109 a/109 b, and the first/second IC region isolation structures 236 a/236 b. The dishing prevention dummy gates 114 may also be arranged elsewhere in the first IC region 112 a and the second IC region 112 b. For example, the dishing prevention dummy gates 114 may be placed over the first/second inner highly doped region 111 a/111 b or the first/second outer highly doped region 113 a/113 b. By placing the dishing prevention dummy gates 114 various locations across the first IC region 112 a and the second IC region 112 b, the dishing prevention dummy gates 114 may prevent unwanted dishing from occurring over the first device region 102 a and the second device region 102 b during a subsequent CMP process by acting as support pillars for the ILD layer 204. Accordingly, by reducing the amount of dishing, the performance of the first devices 104 a and the second devices 104 b may be improved and the cost of manufacturing the IC 200 may be reduced.

The dishing prevention dummy gates 114 are typically incorporated into the same processing steps that are used to form the gate stacks of the first device region 102 a and the second device region 102 b. Thus, in some embodiments, the dishing prevention dummy gates 114 include a dummy gate dielectric 232, a dummy gate 234, and sidewall spacers 224. The dummy gate 234 may comprises, for example, polysilicon, aluminum, copper, tantalum, or some other suitable material.

Further, to ensure uniform removal of the ILD layer 204, the dishing prevention dummy gates 114 may have similar geometrical dimensions (e.g., a similar gate electrode height/width/depth, gate oxide height/width/depth, and/or sidewall spacer height/width/depth) as the features of the devices 104 a/104 b nearest the dishing prevention dummy gates 114. For example, in some embodiments, the first devices 104 a are low voltage devices and the device gate electrode 222 may comprise metal and the device gate dielectric 220 may comprise a high-k dielectric, which may be referred to as a high-k metal gate (HKMG) devices. Accordingly, the dishing prevention dummy gates 114 proximate the HKMG devices may have similar features and dimensions as the HKMG devices in the first device region 102 a. On the other hand, the second devices 104 b may be mid-voltage devices and the device gate electrode 222 may be a fully silicided (FUSI) gate. Accordingly, the dishing prevention dummy gates 114 proximate the FUSI gate devices may have similar features and dimensions as the FUSI gate devices in the second device region 102 b. In other embodiments, additional processes (e.g., photolithography, etching, anneals) may be used to form the dishing prevention dummy gates, such that the features and geometries of the dishing prevention dummy gates 114 are not similar to the features of the proximate devices.

In some embodiments, the dummy gate dielectrics 232 of the dishing prevention dummy gates 114 disposed in the first IC region 112 a have a first dummy gate dielectric height, h₁, and the device gate dielectrics 220 of the first devices 104 a have a first device gate dielectric height, h₂. The dummy gate dielectrics 232 of the dishing prevention dummy gates 114 disposed in the second IC region 112 b have a second dummy gate dielectric height, h₃, and the device gate dielectrics 226 of the second devices 104 b have a second device dielectric height, h₄. In some embodiments, the first dummy gate dielectric height, h₁, is substantially the same as the first device gate dielectric height, h₂, and the second dummy gate dielectric height, h₃, is substantially the same as the second device dielectric height, h₄.

Because some of the features described above are arranged in a similar manner in both the first IC region 112 a and the second IC region 112 b, some features are only described with reference to the first IC region 112 a. However, it will be appreciated that in some embodiments the description of these features also pertains to similar features in the second IC region 112 b.

FIG. 3A illustrates a cross-sectional view of some more detailed embodiments of an integrated circuit 300A comprising first and second IC regions having dishing prevention dummy gates.

In some embodiments, the IC 300A comprises an interconnect structure 308 that is arranged over the ILD layer 204. The interconnect structure 308 may comprise a plurality of inter-metal dielectric (IMD) layers 310-311. In some embodiments, a first IMD layer 311 is disposed over a top surface of the ILD layer 204. The IMD layers 310-311 may comprise, for example, one or more layers of an oxide, a low-k dielectric, or an ultra-low-k dielectric. The IMD layers 310-311 may surround contacts 312, metal wires 314, and metal vias 316 that comprise, for example, copper, tungsten, and/or aluminum. For example, the contacts 312 are configured to electrically couple the pair of source/drain regions 216 of the first devices 104 a and the second devices 104 b to a first metal wire 314 of the interconnect structure 308.

An under-bump metallization (UBM) stack 318 is arranged over the interconnect structure 308. In some embodiments, the UBM stack 318 comprises a passivation layer 320 and a UBM layer 322. In some embodiments, the passivation layer 320 comprises one or more layers of SiO₂, silicon nitride (Si₃N₄), polyimide compounds, or other suitable materials. The UBM layer 322 contacts an upper conductive feature (e.g., a contact pad) of the interconnect structure 308. The UBM layer 322 may comprise, for example, aluminum, titanium, tungsten, or some other suitable material. The UBM layer 322 is configured to provide an interface between an overlying solder bump (not shown) and an underlying conductive feature (e.g., a contact pad or a conductive trace) of the interconnect structure 308.

FIG. 3B illustrates a cross-sectional view of some embodiments of an integrated circuit 300B comprising a first IC region having dishing prevention dummy gates and a second IC region having dishing prevention dummy gates disposed proximate a third device region.

The integrated circuit 300B comprises a third device region 324 arranged adjacent to the second IC region 112 b. The third device region 324 may comprise a plurality of third devices 326. In some embodiments, the first IC region 112 a comprises low voltage devices, the second IC region 112 b comprises mid-voltage devices, and the third device region 324 comprises high-voltage devices. In some embodiments, the third device 326 comprises a high voltage n-well 328 disposed within the semiconductor substrate 202 and arranged within a high voltage p-well 330. A pair of source/drain regions 216 are also disposed within the semiconductor substrate 202 and are arranged within the high-voltage n-well 328. A plurality of isolation structures 332 are further disposed within the semiconductor substrate 202 and separate various features (e.g., the pair of source/drain regions 216 from highly doped regions of the high voltage p-well 334) of the third device 326.

The third device 326 may further comprise a high voltage oxide layer 336 that is disposed over the semiconductor substrate 202 and arranged between the pair of source/drain regions 216. A high voltage gate oxide layer 338 is arranged over the high voltage oxide layer 336 and separates the high voltage gate 340 from the high voltage oxide layer 336. In some embodiments, a pair of high voltage sidewall spacers 342 are arranged along sidewalls of the high voltage gate oxide layer 338 and the high voltage gate 340. The interconnect structure 308 and the UBM stack 318 are disposed over the third device region 324 to electrically couple features (e.g., pair of source/drain regions 216, high voltage gate 340, and/or highly doped regions of the high voltage p-well 334) of the third device region 324 to an input/output structure (e.g., a solder bump). In further embodiments, the third device 326 may be, for example, high voltage bipolar junction transistor, a vertical diffused metal oxide semiconductor (VDMOS) device, a laterally diffused metal oxide semiconductor (LDMOS) device, or some other power metal-oxide-semiconductor field-effect transistor (MOSFET).

With reference to FIGS. 4-19, a series of cross-sectional views of some embodiments of a method for forming a first IC region having dishing prevention dummy gates and a second IC region having dishing prevention dummy gates is provided.

As illustrated by FIG. 4, a first deep well region 212 a, a second deep well region 212 b, a first inner isolation structure 107 a, a second inner isolation structure 107 b, a first outer isolation structure 109 a, a second outer isolation structure 109 b, a first IC region isolation structure 236 a, and a second IC region isolation structure 236 b (collectively “isolation structures 107 a/107 b/109 a/109 b/236 a/236 b”) are formed in the semiconductor substrate 202. In some embodiments, prior to forming the isolation structures 107 a/107 b/109 a/109 b/236 a/236 b, the first deep well region 212 a and the second deep well region 212 b are formed in the semiconductor substrate 202. The first deep well region 212 a and the second deep well region 212 b have a first doping type (e.g., p-type) and may, for example, be formed by ion implantation. Moreover, in some embodiments, a process for forming the isolation structures 107 a/107 b/109 a/109 b/236 a/236 b comprise performing an etch into the semiconductor substrate 202 to form trenches in the semiconductor substrate 202, and subsequently filling the trenches with a dielectric material. In yet further embodiments, the first inner isolation structure 107 a demarcates a first device region 102 a, and the second inner isolation structure 107 b demarcates a second device region 102 b.

As illustrated by FIG. 5, a first device well 206 a and a second device well 206 b are formed within the semiconductor substrate 202. The first device well 206 a and the second device well 206 b have a second doping type (e.g., n-type). In some embodiments, the second doping type is different than the first doping type, and in other embodiments the first doping type and the second doping type are the same. The first device well 206 a and the second device well 206 b may, for example, be formed by ion implantation.

As illustrated by FIG. 6, a first inner ring-shaped well 106 a, a second inner ring-shaped well 106 b, a first outer ring-shaped well 108 a, and a second outer ring-shaped well 108 b are formed within the semiconductor substrate 202. In some embodiments, the first inner ring-shaped well 106 a and the second inner ring-shaped well 106 b have the first doping type (e.g., p-type), and the first outer ring-shaped well 108 a and the second outer ring-shaped well 108 b have the second doping type (e.g., n-type). The first inner ring-shaped well 106 a, the second inner ring-shaped well 106 b, the first outer ring-shaped well 108 a, and the second outer ring-shaped well 108 b may, for example, be formed by ion implantation. Accordingly, the first inner ring-shaped well 106 a and the second inner ring-shaped well 106 b act as a protection element (i.e., a guard ring) for devices disposed on the IC by collecting unwanted electrical signals that may propagate in/out of the first device region 102 a or the second device region 102 b, respectively, and disrupt (e.g., latch-up, unwanted activation, etc.) the function of the devices disposed on the IC. Further, the first inner ring-shaped well 106 a in combination with the first outer ring-shaped well 108 a and the second inner ring-shaped well 106 b in combination with the second outer ring-shaped well 108 b may provide junction isolation that prevents unwanted current from flowing in/out the first device region 102 a or the second device region 102 b, respectively, and disrupting the function of devices disposed on the IC.

As illustrated by FIG. 7, a first gate dielectric layer 702 is formed over the semiconductor substrate 202. The first gate dielectric layer 702 is disposed over both the first IC region 112 a and the second IC region 112 b. The first gate dielectric layer 702 may, for example, be formed by thermal oxidation, chemical vapor deposition (CVD), physical vapor deposition (PVD), sputtering, or the like.

As illustrated by FIG. 8, a first photoresist mask 802 is formed over the first gate dielectric layer 702 by depositing a first photoresist layer (e.g., by a spin-on process) and selectively patterning the first photoresist layer (e.g., by a photolithography process). In some embodiments, the first photoresist mask 802 may, for example, be formed over the first IC region 112 a but not over the second IC region 112 b, or vice versa. With the first photoresist mask 802 in place, a first etch 804 (e.g., dry etch or wet etch) is performed into the first gate dielectric layer (702 of FIG. 7) to form a patterned first gate dielectric layer 806. In some embodiments, after the first etch 804 is performed, the first photoresist mask 802 is stripped away.

As illustrated by FIG. 9, a second gate dielectric layer 902 is formed over the semiconductor substrate 202 and the patterned first gate dielectric layer 806. The second gate dielectric layer 902 may, for example, be formed by thermal oxidation, CVD, PVD, sputtering, or the like. In some embodiments, the second gate dielectric layer 902 has a first upper surface over the first IC region 112 a and a second upper surface over the second IC region 112 b that is a greater distance from the semiconductor substrate 202 than the first upper surface of the second gate dielectric layer 902. In further embodiments, the patterned first gate dielectric layer 806 may have a thickness between about 100 angstrom and about 200 angstrom.

As illustrated by FIG. 10, a conductive layer 1002 is formed over the second gate dielectric layer 902. The conductive layer 1002 may, for example, comprise doped polysilicon, metal, or some other conductive material and may, for example, be formed by CVD, PVD, sputtering, or the like. In some embodiments, the conductive layer 1002 has a first upper surface over the first IC region 112 a and second upper surface over the second IC region 112 b that is a greater distance from the semiconductor substrate 202 than the first upper surface of the conductive layer 1002. In further embodiments, the second gate dielectric layer 902 may have a thickness between about 10 angstrom and about 20 angstrom.

Although FIG. 10 illustrates the conductive layer 1002 being formed on the second gate dielectric layer 902, in some additional embodiments, additional gate dielectric layers may be formed prior to forming the conductive layer 1002. A second photoresist mask 1004 is formed over the conductive layer 1002 by depositing a second photoresist layer (e.g., by a spin-on process) and selectively patterning the second photoresist layer (e.g., by a photolithography process). In some embodiments, the second photoresist mask 1004 is patterned such that the second photoresist mask 1004 covers portions of the conductive layer 1002 between isolation structures 107 a/107 b/109 a/109 b/236 a/236 b. In other embodiments, the second photoresist mask 1004 is patterned such that the second photoresist mask 1004 covers portions of the conductive layer 1002 over the isolation structures 107 a/107 b/109 a/109 b/236 a/236 b.

As illustrated by FIG. 11, with the second photoresist mask 1004 in place, a second etch 1102 (e.g., dry etch or wet etch) is performed into the conductive layer 1002, the second gate dielectric layer 902, and the patterned first gate dielectric layer 806 to form a plurality of dishing prevention dummy gate stacks 1108, a first device gate stack 1104 a, and a second device gate stack 1104 b. The first device gate stack 1104 a comprises a first device gate electrode 222′ disposed over a first device gate dielectric 220, and the second device gate stack 1104 b comprises a second device gate electrode 228′ disposed over a second device gate dielectric 226. The plurality of dishing prevention dummy gate stacks 1108 each comprise a dummy gate 234′ disposed over a dummy gate dielectric 232. In some embodiments, the apostrophe mark in FIGS. 11-17 indicates that the first device gate electrode 222′, the second device gate electrode 228′, and the dummy gate 234′ comprise an intermediate material (e.g., polysilicon) that may undergo a subsequent process (e.g., poly-gate replacement (RPG) high-k metal gate (HKMG) process, a fully silicided (FUSI) process, etc.) step that alters the composition of the intermediate material.

Depending on whether the dishing prevention dummy gate stacks 1108 are disposed in the first IC region 112 a or the second IC region 112 b, the dummy gate dielectric 232 will have a height similar to either the first device gate dielectric 220 or the second device gate dielectric 226, respectively. In some embodiments, a plurality of first device gate stacks 1104 a are formed in the first IC region 112 a and a plurality of second device gate stacks 1104 b are formed in the second IC region 112 b. In yet further embodiments, after the second etch 1102 is performed, the second photoresist mask 1004 is stripped away.

As illustrated by FIG. 12, in some embodiments, pairs of lightly-doped source/drain extensions 1202 are formed within the first IC region 112 a and the second IC region 112 b. In some embodiments, the pairs of lightly-doped source/drain extensions 1202 are formed within the semiconductor substrate 202 by, for example, ion implantation while using the dishing prevention dummy gates 114, the first device gate stack 1104 a, and the second device gate stack 1104 b as a mask. Because the dishing prevention dummy gates 114, the first device gate stack 1104 a, and the second device gate stack 1104 b may be used as a mask, the lightly-doped source/drain extensions 1202 may also be formed between the dishing prevention dummy gates 114. In other embodiments, a mask is formed to prevent implantation of the lightly-doped source/drain extensions 1202 between the dishing prevention dummy gates 114. The pairs of lightly-doped source/drain extensions 1202 comprise the first doping type or the second doping type, so that the source/drain extensions 1202 may have the same doping type or a different doping type than the region (e.g., the first inner ring-shaped well 106 a) of semiconductor substrate 202 in which they are disposed.

As illustrated by FIG. 13, sidewall spacers 224 are formed on sidewalls of the dishing prevention dummy gate stacks 1108; the first device gate stack 1104 a; and the second device gate stack 1104 b. In some embodiments, a mask is formed to prevent formation of the sidewall spacers 224 along the dishing prevention dummy gate stacks 1108. The sidewall spacers 224 may, for example, be silicon nitride, silicon dioxide, some other dielectric, or a combination of the foregoing. In some embodiments, a process for forming the sidewall spacers 224 comprises depositing or growing a spacer layer covering and conformally lining the structure in FIG. 11. The spacer layer may, for example, be deposited or grown by CVD, PVD, sputtering, or some other deposition or growth process. Further, in some embodiments, the process comprises performing an etch back into the spacer layer to remove horizontal segments of the spacer layer without removing vertical segments of the spacer layer.

As illustrated by FIG. 14, pairs of source/drain regions 216 are formed in the semiconductor substrate 202 of the first IC region 112 a and the second IC region 112 b. In some embodiments, the pairs of source/drain regions 216 respectively adjoin pairs of the lightly-doped source/drain extensions 218 disposed between dishing prevention dummy gate stacks 1108, the first device gate stack 1104 a, and the second device gate stack 1104 b. In other embodiments, a mask is formed to prevent implantation of the pairs of source/drain regions 216 between two adjacent dishing prevention dummy gate stacks 1108. In some embodiments, the source/drain regions 216 are formed by, for example, ion implantation.

As illustrated by FIG. 15, a ILD layer 204 is formed over the semiconductor substrate 202. The ILD layer 204 may comprise one or more layers of, for example, PSG, BPSG, SiO₂, or some other suitable dielectric. The ILD layer 204 may, for example, be formed by CVD, PVD, sputtering, or one other deposition or growth process, or a combination of the foregoing.

As illustrated by FIG. 16, the ILD layer 204 is planarized by a first planarization process 1602. The first planarization process 1602 may, for example, be a CMP process. The first planarization process 1602 reduces the height of the first device gate electrode 222′, the second device gate electrode 228′, and the dummy gates 234′. Accordingly, a top surface of the first device gate electrode 222′, the second device gate electrode 228′, and the dummy gates 234 are substantially co-planar with a top surface of the ILD layer 204.

As illustrated by FIG. 17, a RPG HKMG process is performed. The dummy gates 234′ disposed in the first IC region 112 a and the first device gate electrode 222′ are replaced with a metal material 1702 (e.g., aluminum, copper, tantalum, or some other conductive material) to form dummy gates 234 in the first IC region 112 a and the first device gate electrode 222. In some embodiments, the dummy gates 234 in the first IC region 112 a may be metal dummy gates 234 and the first device gate electrode 222 may be a first metal device gate electrode 222.

In some embodiments, the RPG HKMG process comprises forming a third photoresist mask 1704 is over the ILD layer 204 in the second IC region 112 b to protect the dummy gates 234′ disposed in the second IC region 112 b and the second device gate electrode 228′ from the RPG HKMG process. In further embodiments, the RPG HKMG process comprises a first etch process to remove the dummy gates 234′ disposed in the first IC region 112 a and the first device gate electrode 222′. After the dummy gates 234′ disposed in the first IC region 112 a and the first device gate electrode 222′ are removed, the metal material 1702 is deposited in the openings in the ILD layer 204 formed by removing the dummy gates 234′ disposed in the first IC region 112 a and the first device gate electrode 222′. Thus, metal dummy gates 234 are formed in the first IC region 112 a, and a first metal device gate electrode 222 is formed. Subsequently, the third photoresist mask 1704 is stripped away.

As illustrated by FIG. 18, in some embodiments, a FUSI process 1802 is performed on the dummy gates 234′ disposed in the second IC region 112 b and the second device gate electrode 228′ to form dummy gates 234 in the second IC region 112 b and the second device gate electrode 228. In some embodiments, the dummy gates 234 in the second IC region 112 b may be fully silicided dummy gates 234 and the second device gate electrode 228 may be a second fully silicided device gate electrode 228. In some embodiments, before the FUSI process 1802 is performed, a second planarization process (e.g., a CMP process) is performed to remove excess metal material 1702 and planarize the dummy gates 234 in the first IC region 112 a and the first device gate electrode 222.

Moreover, in some embodiments, a fourth photoresist mask 1804 is formed over the ILD layer 204 in the first IC region 112 a to protect the dummy gates 234 in the first IC region 112 a and the first device gate electrode 222 from the FUSI process. In some embodiments, the FUSI process may comprise forming a transition metal layer (not shown) (e.g., nickel) over the ILD layer 204 in the second IC region 112 b. After the transition metal is formed, an anneal process is performed that causes the transition metal layer (not shown) to react with the dummy gates 234′ disposed in the second IC region 112 b and the second device gate electrode 228′. Accordingly, fully silicided dummy gates 234 are formed in the second IC region 112 b, and the second fully silicided device gate electrode 222 is formed. In some embodiments, a third planarization process (e.g., a CMP process) is performed to planarize the dummy gates 234 in the second IC region 112 b and the second device gate electrode 228.

As illustrated by FIG. 19, a fourth planarization process 1902 is performed on the ILD layer 204. In some embodiments, the fourth planarization process 1902 is a CMP process suitable for planarizing features of a high voltage device region (e.g., 324 of FIG. 3). Due to the parameters of the fourth planarization process 1902, the fourth planarization process 1902 may cause dishing to occur in the first IC region 112 a and the second IC regions 112 b, which may result in decreased device performance. However, because the dishing prevention dummy gates 114 have been formed in the first IC region 112 a and the second IC region 112 b, the amount of dishing that occurs in the first IC region 112 a and the second IC region 112 b is reduced. Moreover, because the dummy gates 234 in the first IC region 112 a and the first device gate electrode 222 are formed via a RPG HKMG process and the dummy gates 234 in the second IC region 112 b and the second device gate electrode 228 are formed via a FUSI process, the amount of dishing that occurs over the first IC region 112 a and the second IC region 112 b may be further controlled and reduced. Thus, device performance may increase and the cost of manufacturing may be reduced.

With reference to FIG. 20, a flowchart 2000 of some embodiments of the method for forming a first IC region having dishing prevention dummy gates and a second IC region having dishing prevention gate is provided. While the flowchart 2000 of FIG. 20 is illustrated and described herein as a series of acts or events, it will be appreciated that the illustrated ordering of such acts or events is not to be interpreted in a limiting sense. For example, some acts may occur in different orders and/or concurrently with other acts or events apart from those illustrated and/or described herein. Further, not all illustrated acts may be required to implement one or more aspects or embodiments of the description herein, and one or more of the acts depicted herein may be carried out in one or more separate acts and/or phases.

At 2002, deep well regions and isolation structures are formed in the semiconductor substrate. FIG. 4 illustrates a cross-sectional view of some embodiments corresponding to act 2002.

At 2004, device well regions are formed in a semiconductor substrate. FIG. 5 illustrates a cross-sectional view of some embodiments corresponding to act 2004.

At 2006, inner ring-shaped wells and outer ring-shaped wells are formed in the semiconductor substrate. FIG. 6 illustrates a cross-sectional view of some embodiments corresponding to act 2006.

At 2008, gate oxide layers and a conductive layer are formed over the semiconductor substrate. FIGS. 7-10 illustrate a series of cross-sectional views of some embodiments corresponding to act 2008.

At 2010, dishing prevention dummy gate stacks having dishing prevention dummy gates, a first device gate stack having a first device gate electrode, and a second device gate stack having a second device gate electrode are formed. FIG. 11 illustrates a cross-sectional view of some embodiments corresponding to act 2010.

At 2012, pairs of source/drain extensions are formed within the semiconductor substrate. FIG. 12 illustrates a cross-sectional view of some embodiments corresponding to act 2012.

At 2014, sidewall spacers are formed along sidewalls of the dishing prevention dummy gate stacks, the first device gate stack, and the second device gate stack. FIG. 13 illustrates a cross-sectional view of some embodiments corresponding to act 2014.

At 2016, pairs of source/drain regions are formed within the semiconductor substrate. FIG. 14 illustrates a cross-sectional view of some embodiments corresponding to act 2016.

At 2018, an interlayer dielectric (ILD) layer is formed over the semiconductor substrate. FIG. 15 illustrates a cross-sectional view of some embodiments corresponding to act 2018.

At 2020, the ILD layer is planarized to expose the dishing prevention dummy gates, the first device gate electrode, and the second device gate electrode. FIG. 16 illustrates a cross-sectional view of some embodiments corresponding to act 2020.

At 2022, the dishing prevention dummy gates in a first IC region are replaced with a metal material to form metal dummy gates in the first IC region, and the first device gate electrode is replace with the metal material to from a first metal device gate electrode. FIG. 17 illustrates a cross-sectional view of some embodiments corresponding to act 2022.

At 2024, the dishing prevention dummy gates in a second IC region are fully silicided to form fully silicided dummy gates in the second IC region, and the second device gate electrode is fully silicided to form a second fully silicided device gate electrode. FIG. 18 illustrates a cross-sectional view of some embodiments corresponding to act 2024.

At 2026, the ILD layer is planarized. FIG. 19 illustrates a cross-sectional view of some embodiments corresponding to act 2026.

In view of the foregoing, some embodiments of the present application provide an integrated circuit (IC) having an inner ring-shaped isolation structure disposed in a semiconductor wafer, in which the inner ring-shaped isolation structure demarcates a device region. An inner-ring shaped well is disposed in the semiconductor and surrounds the inner ring-shaped isolation structure. A plurality of dummy gates are arranged over the inner ring-shaped well, in which the plurality of dummy gates are disposed within an interlayer dielectric (ILD) layer.

Further, other embodiments of the present application provide an integrated circuit having a first IC region and a second IC region. The first IC region includes a first inner ring-shaped isolation structure disposed in a semiconductor substrate, in which the first inner ring-shaped isolation structure demarcates a first device region. The first IC region further includes a first inner-ring shaped well that is disposed in the semiconductor substrate and surrounds the first inner ring-shaped isolation structure. In addition, the first IC region includes a first dishing prevention dummy gate arranged over the first inner ring-shaped well, in which the first dishing prevention dummy gate is disposed in a dielectric layer. The second IC region includes a second inner ring-shaped isolation structure disposed in the semiconductor substrate, in which the second inner ring-shaped isolation structure demarcates a second device region. The second IC region further includes a second inner-ring shaped well that is disposed in the semiconductor substrate and surrounds the second inner ring-shaped isolation structure. In addition, the second IC region includes a second dishing prevention dummy gates arranged over the second inner ring-shaped well, in which the second dishing prevention dummy gate is disposed in the dielectric layer.

Further yet, other embodiments of the present application provide a method for forming an integrated circuit (IC). The method includes forming a first inner ring-shaped isolation structure in a semiconductor substrate, in which the first inner ring-shaped isolation structure demarcates a first device region. A first inner-ring shaped well is formed in the semiconductor substrate and surrounds the first inner ring-shaped isolation structure. A second inner ring-shaped isolation structure that is laterally spaced from the first inner ring-shaped isolation structure is formed in the semiconductor substrate, in which the second inner ring-shaped isolation structure demarcates a second device region. A second inner ring-shaped well is formed in the semiconductor substrate and surrounds the second inner ring-shaped isolation structure. A first dummy gate is formed over the first inner ring-shaped well. A first device gate electrode is formed over the first device region. A second dummy gate is formed over the second inner ring-shaped well. A second device gate electrode is formed over the second device region. The first dummy gate and the first device gate electrode are removed and replaced with a conductive material. The second dummy gate and the second device gate electrode are reacted with a transition metal. A chemical-mechanical planarization (CMP) process is performed on the IC.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. 

What is claimed is:
 1. A method for forming an integrated circuit (IC), comprising: forming a first ring-shaped isolation structure in a first region of a semiconductor substrate; forming a second ring-shaped isolation structure in a second region of the semiconductor substrate different than the first region; forming a first gate dielectric layer over the first and second regions of the semiconductor substrate; removing a first portion of the first gate dielectric layer that is over the first region of the semiconductor substrate, thereby leaving a second portion of the first gate dielectric layer in place over the second region of the semiconductor substrate; forming a second gate dielectric layer over the first region of the semiconductor substrate and the second portion of the first gate dielectric layer; forming a conductive layer over the second gate dielectric layer; and patterning the conductive layer, the second portion of the first gate dielectric layer, and the second gate dielectric layer, thereby forming a first dummy gate stack over the first region of the semiconductor substrate and a second dummy gate stack over the second region of the semiconductor substrate.
 2. The method of claim 1, further comprising: forming a ring-shaped well in the semiconductor substrate and laterally surrounding the first ring-shaped isolation structure.
 3. The method of claim 1, further comprising: forming sidewall spacers over the semiconductor substrate and along sides of the first and second dummy gate stacks.
 4. The method of claim 1, further comprising: forming an interlayer dielectric (ILD) layer over the semiconductor substrate and the first and second dummy gate stacks; and removing an upper portion of the ILD layer to expose upper surfaces of the first and second dummy gate stacks.
 5. The method of claim 1, wherein: the conductive layer is formed with a first upper surface over the first region of the semiconductor substrate and a second upper surface over the second region of the semiconductor substrate; and the second upper surface of the conductive layer is vertically spaced a greater distance from the semiconductor substrate that the first upper surface of the conductive layer.
 6. The method of claim 5, further comprising: before the conductive layer, the second portion of the first gate dielectric layer, and the second gate dielectric layer are patterned, performing a planarization process on the conductive layer so that the conductive layer has a planar uppermost surface that extends laterally over both the first and second regions of the semiconductor substrate.
 7. The method of claim 1, wherein patterning the conductive layer, the second portion of the first gate dielectric layer, and the second gate dielectric layer also forms a first device gate electrode and a first device gate dielectric structure within an inner perimeter of the first ring-shaped isolation structure and also forms a second device gate electrode and a second device gate dielectric structure within an inner perimeter of the second ring-shaped isolation structure.
 8. The method of claim 7, wherein: the first dummy gate stack comprises a first segment of the second gate dielectric layer; the first device gate dielectric structure comprises a second segment of the second gate dielectric layer; the second dummy gate stack comprises a third segment of the second gate dielectric layer and a first segment of the second portion of the first gate dielectric layer; the third segment of the second gate dielectric layer overlies the first segment of the second portion of the first gate dielectric layer; the second device gate dielectric structure comprises a fourth segment of the second gate dielectric layer and a second segment of the second portion of the first gate dielectric layer; and the fourth segment of the second gate dielectric layer overlies the second segment of the second portion of the first gate dielectric layer.
 9. The method of claim 8, further comprising: forming sidewall spacers over the semiconductor substrate and along sides of the first dummy gate stack, the second dummy gate stack, the first device gate electrode, and the second device gate electrode.
 10. A method for forming an integrated circuit (IC), comprising: forming a first ring-shaped isolation structure in a first region of a semiconductor substrate; forming a second ring-shaped isolation structure in a second region of the semiconductor substrate different than the first region, wherein the first ring-shaped isolation structure is spaced from the second ring-shaped isolation structure; forming a ring-shaped well in the semiconductor substrate and laterally surrounding the first ring-shaped isolation structure; forming a first dummy gate stack in the first region of the semiconductor substrate and a second dummy gate stack over the second region of the semiconductor substrate; replacing a dummy gate of the first dummy gate stack with a conductive material, thereby forming a conductive dummy gate over a dummy gate dielectric structure of the first dummy gate stack; and performing a silicide process on a dummy gate of the second dummy gate stack, thereby forming a fully silicided (FUSI) dummy gate over a dummy gate dielectric structure of the second dummy gate stack.
 11. The method of claim 10, wherein replacing the dummy gate of the first dummy gate stack with the conductive material comprises: performing an etching process that removes the dummy gate of the first dummy gate stack, thereby forming an opening over the dummy gate dielectric structure of the first dummy gate stack; and filling the opening with the conductive material, thereby forming the conductive dummy gate, wherein an upper surface of the dummy gate of the second dummy gate stack is protected during the etching process.
 12. The method of claim 11, further comprising: forming an interlayer dielectric (ILD) layer over the semiconductor substrate, the first dummy gate stack, and the second dummy gate stack; removing an upper portion of the ILD layer to expose the dummy gate of the first dummy gate stack and the dummy gate of the second dummy gate stack; and after the upper portion of the ILD layer is removed, forming a masking layer over the ILD layer and the dummy gate of the second dummy gate stack.
 13. The method of claim 10, wherein the silicide process comprises: depositing a transition metal layer on the dummy gate of the second dummy gate stack; and heating the transition metal layer so that the transition metal layer reacts with the dummy gate of the second dummy gate stack, thereby forming the FUSI dummy gate, wherein an upper surface of the dummy gate of the first dummy gate stack is covered during the deposition of the transition metal layer.
 14. The method of claim 13, further comprising: forming an interlayer dielectric (ILD) layer over the semiconductor substrate, the first dummy gate stack, and the second dummy gate stack; removing an upper portion of the ILD layer to expose the dummy gate of the first dummy gate stack and the dummy gate of the second dummy gate stack; and after the upper portion of the ILD layer is removed, forming a masking layer over the ILD layer and the dummy gate of the first dummy gate stack.
 15. The method of claim 10, further comprising: forming an interlayer dielectric (ILD) layer over the semiconductor substrate, the first dummy gate stack, and the second dummy gate stack; removing an upper portion of the ILD layer to expose the dummy gate of the first dummy gate stack and the dummy gate of the second dummy gate stack; after the upper portion of the ILD layer is removed, forming a first masking layer covering the ILD layer and the dummy gate of the second dummy gate stack, wherein the conductive dummy gate is formed with the first masking layer covering the dummy gate of the second dummy gate stack; removing the first masking layer; and after the first masking layer is removed, forming a second masking layer covering the ILD layer and the conductive dummy gate, wherein the FUSI dummy gate is formed with the second masking layer covering the conductive dummy gate.
 16. The method of claim 10, further comprising: forming an interlayer dielectric (ILD) layer over the semiconductor substrate, the first dummy gate stack, and the second dummy gate stack; removing an upper portion of the ILD layer to expose the dummy gate of the first dummy gate stack and the dummy gate of the second dummy gate stack; after the upper portion of the ILD layer is removed, forming a first masking layer covering the ILD layer and the dummy gate of the first dummy gate stack, wherein the FUSI dummy gate is formed with the first masking layer covering the dummy gate of the first dummy gate stack; removing the first masking layer; and after the first masking layer is removed, forming a second masking layer covering the ILD layer and the FUSI dummy gate, wherein the conductive dummy gate is formed with the second masking layer covering the FUSI dummy gate.
 17. The method of claim 10, wherein the conductive material is a metal.
 18. A method for forming an integrated circuit (IC), comprising: forming a first ring-shaped isolation structure in a semiconductor substrate; forming a second ring-shaped isolation structure in the semiconductor substrate and spaced from the first ring-shaped isolation structure; forming a ring-shaped well in the semiconductor substrate and laterally surrounding the first ring-shaped isolation structure; forming a gate dielectric layer over the semiconductor substrate and covering both the first ring-shaped isolation structure and the second ring-shaped isolation structure; forming a conductive layer over the gate dielectric layer; and patterning the conductive layer and the gate dielectric layer, thereby forming a first device gate electrode and a first device gate dielectric structure within an inner perimeter of the first ring-shaped isolation structure, a second device gate electrode and a second device gate dielectric structure within an inner perimeter of the second ring-shaped isolation structure, a first dummy gate stack laterally between the first ring-shaped isolation structure and the second ring-shaped isolation structure, and a second dummy gate stack laterally between the first ring-shaped isolation structure and the second ring-shaped isolation structure.
 19. The method of claim 18, further comprising: forming a third ring-shaped isolation structure in the semiconductor substrate and laterally surrounding the first ring-shaped isolation structure, wherein the first dummy gate stack is formed directly over the third ring-shaped isolation structure.
 20. The method of claim 19, further comprising: forming a fourth ring-shaped isolation structure in the semiconductor substrate and laterally surrounding the second ring-shaped isolation structure, wherein the second dummy gate stack is formed directly over the fourth ring-shaped isolation structure. 